A conventional fuse includes a non-conductive tube (1), as shown in FIG. 1A, which connects one end with a metal cap (3) by welding with tin (2). A resistance filament (4) is provided therein. And then, another cap (3′) is welded on the other end of the non-conductive tube (1) with tin (2′) to produce a complete fuse, as in FIGS. 1B and 1C. In such manufacturing procedure, when the cap (3′) is being welded, the temperature will increase and cause air in the tube (1) to expand and be pushed outwardly. The tin (2′) is usually extruded and exposed outside the metal cap (3′) as in FIG. 1D. This fuse is useless and is only a defeat work.